This invention relates to steel flanged wheel rims for motorized bicycles or two-wheeled vehicles and a process for producing the rims.
There have been proposed and practically employed a variety of steel flanged wheel rims and one of the prior art steel flanged wheel rims is produced by curling a steel plate blank 2 at the opposite side edges thereof by a series of rolls in a roll-type shaping machine so as to form a pair of hollow ears 3, 3 extending radially and outwardly in a complete wheel rim, welding the free ends of the curled hollow ears to adjacent areas of the blank, recessing the center area of the width of the blank so as to form a tire receiving semi-circular recess 6, bending the processed blank into a ring shape, cutting the ring to the peripheral length of the beads 7 and flash-butt-welding the cut faces together to make the ring endless (see FIGS. 1 and 2). The thus produced wheel rim 1 then has formed therein a number of spoke holes 8 in the seat of the semi-circular recess 6, wire spokes 10 are inserted into the spoke holes in different three-dimensional orientations, and a hub is then connected to the other ends of the spokes.
In a motorized bicycle or two-wheeled vehicle which has been developed recently, as shown in FIG. 3, plate spokes 11 have been frequently employed in place of the conventional wire spokes 10 and thus, to be used in conjunction with the plate spokes 11, the rim is required to have a flange. The conventional rim 12 as shown in the FIG. 3 is produced by bending an extruded or drawn preformed aluminum alloy blank by a bending roll. However, although aluminum alloy has a high ductility and can be easily bent, since the metal is expensive and employed in the form of a preformed blank, the material expense for such a rim is high, and aluminum is inferior to steel in workability for various applications. Therefore, a steel flanged wheel rim is highly desired.
In order to meet this desire, the steel flanged wheel rim 13 as shown in FIG. 4 has been proposed. Like the conventional wheel rim 1 as described in connection with FIGS. 1 and 2, the steel flanged wheel rim includes the pair of spaced and parallel hollow ears 14, 14, beads 15, 15 and semi-circular recess 16, but the rim 13 further has a flange 17 of T-shaped cross-section welded to the semi-circular recess 16 on the side thereof opposite to the hollow ears 14, 14. The provision of the separate flange 17 on the rim proper makes the production procedure complicated and increases the production cost. Furthermore, when the preformed rim blank is bent into a ring shape, the leg portions 17a, 17a of the flange 17 tend to corrugate and thus, the flange 17 is not applicable to small diameter wheel rims.